FIG. 28 illustrates a hydraulic excavator 10, which is a work machine. The hydraulic excavator 10 includes a lower structure 11, an upper structure 12, a cab 13, a work equipment 14, and a power system 15 that includes an engine. The cab 13, the work equipment 14, and the power system 15 are mounted on the upper structure 12, which is rotatably mounted on the lower structure 11. The power system 15 is covered by a top cover 16, side doors 17,18, and other such components. The side doors 17,18 are mounted by hinges, which will be explained later, so as to be capable of opening and closing, and secured in the closed state by means of a latching device 19.
A conventional door that comprises a set of two metal panels and is used in the field of automobile technology, typically has a structure with a hemmed outer panel, in other words, the outer panel so folded as to curl over the peripheral edge of the inner panel. Therefore, the outer panel, which curls over the inner panel, is usually thinner than the inner panel. However, should this structure be applied to the door panel of a side door 17 or 18 of a work machine, the door panel becomes too weak to withstand an impact from the outside.
Cover units exist with such a structure that includes an outer panel of a work machine folded to curl over the peripheral edge of an inner panel. The outer panel is formed of a plate material having the same thickness as that of the inner panel (e. g. See Japanese Laid-open Patent Publication No. 9-228412 (page 3, and FIGS. 7 and 8) (“JP '412”)).
Various examples also exist of an engine cover of a work machine with a lining that is a sound insulating material or a sound absorbing material attached to the inner side of the cover body of the engine cover (e. g. See Japanese Patent No. 3457804 (page 2, and FIG. 1) (“JP '804”).
A cover unit disclosed in JP '412 has an outer panel and an inner panel that are of the same thickness. Therefore, should both panels be made thinner in order to make the cover unit compact, the panels are easily dented by an external impact. On the other hand, making both panels thicker in order to prevent this problem presents the difficulty of increased weight and costs.
The engine cover disclosed in JP '804 requires that sufficient strength be provided by the cover body alone. This requirement not only makes the cover body heavier but also presents the difficulty of ensuring sufficient strength.
In order to solve the above problems, an object of the invention is to provide a door panel that is light in weight and has sufficient strength.